CHnF4-n与O3吸氢反应途径和速率常数计算

用量子化学方法, 从理论上探讨了CHnF4-n(n=2,3)与臭氧反应的微观机理, 并计算了各反应在不同温度下的速率常数.     

硝酸氯在冰表面上反应的研究

对硝酸氯与一，二，三个水分子的反应作为硝酸氯在冰表面上反应的模型进行了理论研究．MP2     

Air quality monitoring network design to control nitrogen dioxide and ozone, applied in Malaga, Spain

Air monitoring networks are necessary to assess air quality in order to reduce pollution to levels which minimize harmful effects on human health and the environment. This paper describes a method to design or optimize air quality monitoring networks for nitrogen dioxide and ozone and its application in Malaga, a medium large city located in Andalusia, southern Spain, with traffic being the main source of air pollution. The completion of this method revealed that the old assessment network in Malaga was badly designed and made it possible to determine that one traffic-orientated and one background control station were necessary for NO₂ assessment in Malaga, as well as two control stations for O₃. First the number of stations necessary is obtained from historical data. Sampling campaigns with passive diffusion samplers at 74 sites were then carried out to obtain information on the pollution distribution in Malaga. The average concentrations found for NO₂ and O₃ were 22.8 μg/m³ and 64.3 μg/m³ respectively. Maximum values of up to 42.2 μg/m³ NO₂ were found in Malaga city centre and O₃ reached 91.5 μg/m³ downwind from the emission source. After spatial interpolation of the obtained values with Geographical Information Systems, a selection of the best locations for the monitoring stations was made, in line with the macro- and microscale siting requirements of the European Directive 2008/50/EC on ambient air quality and cleaner air for Europe.     

Phase equilibrium for clathrate hydrates formed from an ozone + oxygen gas mixture coexisting with carbon tetrachloride or 1,1-dichloro-1-fluoroethane

This paper reports an attempt at acquiring phase-equilibrium pressure (p) versus temperature (T) data for ozone-containing clathrate hydrates formed from an ozone + oxygen gas mixture, a hydrophobic hydrate-forming liquid, and water in the liquid state. For dealing with ozone (O₃), a chemically unstable material continuously decaying to oxygen (O₂) in the gas phase, we devised a new method, i.e., a modified pressure-search method, to determine the equilibrium p-T conditions while maintaining the ozone concentration in the gas phase nearly constant by repeatedly replacing the contents of the gas phase with a freshly generated O₃ + O₂ mixture. Using carbon tetrachloride (CCl₄) as the hydrophobic hydrate-forming liquid, we obtained equilibrium p-T data in the range of 0.167 MPa ≤ p ≤ 0.361 MPa and 275.6 K ≤ T ≤ 277.3 K in the presence of a gas phase containing O₃ at the molar concentration of 6.9 ± 0.8%. We also obtained, for comparison, the corresponding p-T data, using pure O₂ gas, instead of the O₃ + O₂ mixture, and the conventional pressure-search method. The two data groups obtained from the O₃-containing and O₃-free systems, respectively, show simple, mutually consistent p-T relations each well fitted by the Clausius-Clapeyron equation assuming a constant enthalpy of hydrate dissociation. The paper also describes our additional attempt at obtaining equilibrium p-T data using 1,1-dichloro-1-fluoroethane (R141b) as a substitute for CCl₄. Because of the partial decomposition of R141b due to the coexistence of O₃ and water, however, we obtained only limited data which are tentative in nature.     

An indoor air purification technology using a non-thermal plasma reactor with multiple-wire-to-wire type electrodes and a fiber air filter

For indoor air purification, long-term operation of the air purifier induces the growth of germs and the proliferation of molds, and results in the performance degradation of the air filter. Non-thermal plasma technology could be an effective countermeasure against these problems. Ozone generated by the electric discharge has significant germicidal power and does not produce secondary residual contaminants. Electrostatic force can enable the air filter to function as an electric precipitator. In this study, a non-thermal plasma reactor with wire-wire type electrodes and an air filter is investigated experimentally to improve the performance of the used air filter.     

An evaluation of infrared microwindows for ozone retrievals using the Eureka Bruker 125HR Fourier transform spectrometer

A Bruker 125HR Fourier transform spectrometer was installed at the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Nunavut, Canada in the summer of 2006 to study atmospheric composition. Using the optimal estimation method, typically over a limited spectral region called a microwindow, information about the vertical distribution of trace gas species that have absorption bands in the mid-infrared spectral range can be retrieved. Total and partial columns can also be determined to show the temporal evolution of the target gas. For ozone in particular, retrievals have been performed using several of its many mid-infrared absorption features, resulting in a lack of consistency in the literature in the microwindows chosen for retrievals. This work focuses on the optimization of the ozone retrieval, assessing a set of 22 microwindows between 780 and 3052 cm⁻¹ to determine which is best suited to conditions at Eureka. The 1000-1004.5 cm⁻¹ spectral interval is shown to be the most sensitive to both the stratosphere and troposphere. This microwindow gives the highest number of degrees of freedom for signal (∼7 for total column), and the smallest total error (4.3%) compared with 21 other spectral regions. Retrievals performed with this microwindow agree well with results obtained from other instruments on-site. Total column ozone measured by the Bruker 125HR in this microwindow agreed to 2% with two other Fourier transform spectrometers, to 0.7% with a Brewer spectrophotometer, to 8% with a SAOZ UV-VIS spectrometer, and to 7% with ozone sondes.     

Thermal, ozone and gamma ageing of styrene butadiene rubber and poly(ethylene-co-vinyl acetate) blends

Ageing behaviour of SBR/EVA blends due to the effects of heat, ozone, and gamma radiation was studied with reference to blend ratio, three crosslinking systems (sulfur, peroxide and mixed) and a compatibiliser (SEBS-g-MA). It was found that an increase in the EVA content of the blends enhanced the ageing characteristics. Among the different crosslinking systems, a peroxide cured system exhibited the best retention of properties even after severe ageing. Tensile strength of peroxide cured SBR/EVA blends increased slightly after ageing for three days at 70 °C due to continued crosslinking, whereas tensile strength of all blends decreased on ageing at 100 °C. Compatibilisation with SEBS-g-MA improved the thermal, gamma and water ageing resistance of SBR/EVA blends.     

Development and validation of passive samplers for atmospheric monitoring of SO2, NO2, O3 and H2S in tropical areas

Traditionally the monitoring of atmospheric pollutants is aimed at managing accidents and short-term actions for the protection of human health on local and regional scales. These monitoring networks required continuous measurements with high time resolution, involving costly equipment, operation and maintenance. More recent simulations with mathematical models and scenario-building on regional, continental and global scales, as well as studies of environmental personal exposure are demanding three main types of monitoring design, where need for special resolution surpasses the one of temporal resolution: remote places, where no electric power nor trained human resources are available; validation of dispersion simulation by mathematical modeling on regional to larger scales; indoor measurements where people are acting under noise restriction such as residences, school and hospitals. To meet these demands environmental passive samplers for atmospheric gaseous pollutants have been developed and applied for different situations and environments of Brazil. Passive samplers were developed based on molecular diffusion of gas through a static layer of air with fixed filters impregnated with a specific solution for SO₂, NO₂, O₃ and H₂S and used in the following situations: in remote forest area, urban areas with different characteristics - near the sea, with clean ocean air masses coming in and in areas under direct industrial influence. The passive samplers showed good performance when exposed to different types of areas and during different periods: accuracy of measurements, based on standard deviation, were within the recommended limit by the European Union of ± 25% for this type of device and precision below the maximum of 20% cited in the literature, with variation of 2.0 to 16% in the case of these work. The passive devices were able of measuring concentrations very low as those found in the Amazon region (0.58 ± 0.05 µg m^− 3 SO₂ and 1.10 ± 0.07 µg m^− 3 NO₂) and higher concentrations in industrial areas (20.0 ± 1.3 µg m^− 3 SO₂ e 21.0 ± 1.3 µg m^− 3 NO₂).     

Dynamic solid phase microextraction sampling for reactive terpenes in the presence of ozone

Dynamic gas sampling using solid phase microextraction (SPME) was evaluated for recovery of reactive terpenes and terpenoids in the presence of ozone. For limonene, α-terpineol and dihydromyrcenol in the 20-60 ppb range, this method achieves >80% recovery for ozone mixing ratios up to 100 ppb. Both the experimental results and a model analysis indicate that higher ozone concentrations and longer sampling times result in lower percent recovery. Typically greater than 90% recovery and ppb level method detection limits were achieved with a 5 min sample time. Increasing the flow rate from 100 to 400 sccm flow (5-20 cm s⁻¹) through the active sampler did not significantly affect sensitivity or recovery in most cases, probably due to negligible mass-transfer improvements. The recovery for each compound improves when sampling from a mixture of different species than that from a single compound sample. This may be due to competition for ozone amongst adsorbed species. Dynamic SPME sampling can improve detection and quantification of terpenes in reactive environments, especially for low vapor pressure (<5 mm Hg at 25 °C) compounds that can be adsorbed to ozone scrubbers used in other methods.